| 时间 | 值 （%） | 世界排名 |
|---|---|---|
| 2016 | 17.4 | 151 |
| 2015 | 17.3 | 151 |
| 2014 | 17.1 | 151 |
| 2013 | 16.8 | 158 |
| 2012 | 16.6 | 159 |
| 2011 | 16.5 | 161 |
| 2010 | 16.5 | 163 |
| 2009 | 16.6 | 165 |
| 2008 | 16.8 | 165 |
| 2007 | 17.1 | 163 |
| 2006 | 17.3 | 164 |
| 2005 | 17.4 | 167 |
| 2004 | 17.6 | 168 |
| 2003 | 17.8 | 170 |
| 2002 | 17.9 | 171 |
| 2001 | 18.1 | 172 |
| 2000 | 18.4 | 173 |
| 1999 | 18.6 | 172 |
| 1998 | 18.7 | 174 |
| 1997 | 18.9 | 174 |
| 1996 | 18.9 | 175 |
| 1995 | 18.8 | 175 |
| 1994 | 18.7 | 178 |
| 1993 | 18.5 | 182 |
| 1992 | 18.3 | 184 |
| 1991 | 18.1 | 185 |
| 1990 | 17.9 | 187 |
| 1989 | 17.9 | 185 |
| 1988 | 17.9 | 185 |
| 1987 | 17.9 | 186 |
| 1986 | 18 | 186 |